[test][region-alloc] Relocate unit tests to exist alongside source

Change-Id: I24fcabc7c34e1204c42da5d1b39af19f5da5bb09

zircon/system/utest/region-alloc/BUILD.gn → zircon/system/ulib/region-alloc/test/BUILD.gn

@@ -2,6 +2,13 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+group("test") {
+  testonly = true
+  deps = [
+    ":region-alloc",
+  ]
+}
+
 test("region-alloc") {
   sources = [
     "region-alloc-c-api.c",

zircon/system/utest/BUILD.gn

@@ -83,6 +83,7 @@ if (current_cpu != "") {
       "$zx/system/ulib/minfs/test",
       "$zx/system/ulib/paver:paver-test",
       "$zx/system/ulib/pretty:pretty-test",
+      "$zx/system/ulib/region-alloc/test",
       "$zx/system/ulib/simplehid/test",
       "$zx/system/ulib/storage-metrics/test",
       "$zx/system/ulib/tftp:tftp-test",
@@ -164,7 +165,6 @@ if (current_cpu != "") {
       "qsort",
       "race-tests",
       "ramdisk",
-      "region-alloc",
       "register-state",
       "rtc-lib",
       "runtests-utils",